I know at some point most people in the hobby may at some point experience some sort of tank disaster.. we my time came on Sunday. Here is what happend.

My tank is a 93 Gal Cube (Marineland). I decided to drill the bottom of the tank to use as a closed loop dual canister system. Nothing new, as I have had similar setups in the past with larger tanks. My wife and I spent the entire Saturday taking down the aquarium and setting up a 60 gal cube temporary life support system while we reconfiger the main tank. 10 hours later we had all the occupants back into the main aquarium. Everything went very well except for a small drip at one of the front bulkheads. No problem, a quarter turn of the nut and some silicone fixted that. Over the next 12 hours everything was running well, and the tank looked beautiful. We spent Sunday morning picking up some more bottom dwealing sand sifters and snails. Everything seems to be falling into place we were we just waiting for the last loach to swim out of the bag. A few minutes later, just as the last fish swam out of the bag into the aquarium, I hear a loud 'thud' sound... followed by water dripping. My wife and I imediatly looked at each other thinking the same thing. A few seconds later the sound of water increased and started flowing out all sides of the tank. Thankfully we did not carry the temperary tank downstairs and still have all the hoses, pumps within close proximity. Well my wife and I went into panic mode positioning the temp cube tank on the floor, gathering all the pails / nets, and pumping water, siphoning water into pails, and through the python connected to the sink.

Looking at the damage, the bottom glass cracked from the rear corner bulkhead all the way across diagonally to the other side of the tank. The 4 3/4" bulkheads were positioned in each corner 6" x6" from the corner. I blame the disaster on myself, as I think the problem was caused from over tightening the rear bulkhead. ???

So right now I have the entire system sitting in the middle of the living room floor as a temporary system with all occupants / plants. This sucks as we near the holiday season. So right now my wife and I are searching for a new set up. Hopefully we can get something made befor Christmas.

SeaHorse_Fanatic

12-05-2011, 08:18 PM

First of all, I feel for you. Having a tank blow on you is terrible.

I do agree that it was probably caused by over-tightening the bulkhead. Did you use a wrench or tool or did you tighten by hand. I ALWAYS hand-tighten bulkheads because of this possibility.

Good luck with the rebuild.

Anthony

Bblinks

12-05-2011, 08:41 PM

Sorry to hear about the misfortune. I have heard about several tank bottom blown outs due to modification of a close loop system. funny thing is most of them are on larger marineland tanks like the deep dimension series.

b_james

12-05-2011, 10:13 PM

I do agree that it was probably caused by over-tightening the bulkhead. Did you use a wrench or tool or did you tighten by hand.
Anthony

I used a wrench.. was beyond hand tight. Learned my lesson though :lol:

b_james

12-05-2011, 10:15 PM

Sorry to hear about the misfortune. I have heard about several tank bottom blown outs due to modification of a close loop system. funny thing is most of them are on larger marineland tanks like the deep dimension series.

Is this from people drilling into Deep Dimension tanks? Just wondering becuase I just purchased the Marineland Deep Dimension 150 gal cube that has the overflow. However i was thinking of removing the plastic partitioned so that i can plumb the corner holes directly to my canisters. I would prefer not to use the overflow risking air bubbles in the canister.

sphelps

12-05-2011, 10:34 PM

I can't tell you exactly what caused the failure but I highly doubt it was from over tightening a bulkhead. I do know that when you modify a standard type tank so the bottom looks like Swiss cheese you can no longer rely on support from the edges only, you need to reconfigure how the base is supported typically with foam and a solid base.

Reason being is typical DIY drilling procedures result in a large number of defects around the holes that act as stress concentrations. These stress concentrations greatly reduce safety factor, even a slight surface imperfection can double the local stress. These high local stresses can now easily spread into cracks with a decent load, adding additional support to the base reduces the load and therefore the resulting stress.

Myka

12-06-2011, 01:17 AM

I can't tell you exactly what caused the failure but I highly doubt it was from over tightening a bulkhead. I do know that when you modify a standard type tank so the bottom looks like Swiss cheese you can no longer rely on support from the edges only, you need to reconfigure how the base is supported typically with foam and a solid base.

Reason being is typical DIY drilling procedures result in a large number of defects around the holes that act as stress concentrations. These stress concentrations greatly reduce safety factor, even a slight surface imperfection can double the local stress. These high local stresses can now easily spread into cracks with a decent load, adding additional support to the base reduces the load and therefore the resulting stress.

Agreed.

mark

12-06-2011, 02:41 AM

feel for you, but never understood how over-tightening a bulkhead would crack a tank

reefwars

12-06-2011, 02:43 AM

feel for you, but never understood how over-tightening a bulkhead would crack a tank

especially only a quarter turn past hand tight;)

b_james

12-06-2011, 03:37 PM

The other possibility was that when i drilled the hole, it may have shelled in a way that it caused a small fracture - similar to a chip on a windsheild developing a crack.

Anyways thats all water under the bridge...

b_james

12-06-2011, 03:45 PM

I can't tell you exactly what caused the failure but I highly doubt it was from over tightening a bulkhead. I do know that when you modify a standard type tank so the bottom looks like Swiss cheese you can no longer rely on support from the edges only, you need to reconfigure how the base is supported typically with foam and a solid base.

Reason being is typical DIY drilling procedures result in a large number of defects around the holes that act as stress concentrations. These stress concentrations greatly reduce safety factor, even a slight surface imperfection can double the local stress. These high local stresses can now easily spread into cracks with a decent load, adding additional support to the base reduces the load and therefore the resulting stress.

I would go as far saying it looked like swiss cheese :mrgreen: having four 3/4" bulkheads on a 93 tank IMO is not excessive. There are many factors that may have contributed to the fracture. One possibility could have been the placement of a large 2 foot tall drift wood stump. one of the legs sat within inches of the bulkhead where the fracture occured. Personally I have a feeling it may have more to do with the quality of the hole i drilled. I didnt tape the underneath to minimize shelling.